103 research outputs found
Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at
The light from distant supernovae (SNe) can be magnified through
gravitational lensing when a foreground galaxy is located along the line of
sight. This line-up allows for detailed studies of SNe at high redshift that
otherwise would not be possible. Spectroscopic observations of lensed
high-redshift Type Ia supernovae (SNe Ia) are of particular interest since they
can be used to test for evolution of their intrinsic properties. The use of SNe
Ia for probing the cosmic expansion history has proven to be an extremely
powerful method for measuring cosmological parameters. However, if systematic
redshift-dependent properties are found, their usefulness for future surveys
could be challenged. We investigate whether the spectroscopic properties of the
strongly lensed and very distant SN Ia PS1-10afx at deviates from the
well-studied populations of normal SNe Ia at nearby or intermediate distance.
We created median spectra from nearby and intermediate-redshift
spectroscopically normal SNe Ia from the literature at -5 and +1 days from
light-curve maximum. We then compared these median spectra to those of
PS1-10afx. We do not find signs of spectral evolution in PS1-10afx. The
observed deviation between PS1-10afx and the median templates are within what
is found for SNe at low- and intermediate-redshift. There is a noticeable broad
feature centred at ~\AA{}, which is present only to a
lesser extent in individual low and intermediate redshift SN Ia spectra. From a
comparison with a recently developed explosion model, we find this feature to
be dominated by iron peak elements, in particular, singly ionized cobalt and
chromium.Comment: accepted for publication in section 4. Extragalactic astronomy of
Astronomy and Astrophysic
iPTF16abc and the population of Type Ia supernovae: Comparing the photospheric, transitional and nebular phases
Key information about the progenitor system and the explosion mechanism of
Type Ia supernovae (SNe~Ia) can be obtained from early observations, within a
few days from explosion. iPTF16abc was discovered as a young SN~Ia with
excellent early time data. Here, we present photometry and spectroscopy of the
SN in the nebular phase. A comparison of the early time data with a sample of
SNe~Ia shows distinct features, differing from normal SNe~Ia at early phases
but similar to normal SNe~Ia at a few weeks after maximum light (i.e. the
transitional phase) and well into the nebular phase. The transparency
timescales () for this sample of SNe~Ia range between 25 and 41
days indicating a diversity in the ejecta masses. also weakly correlates
with the peak bolometric luminosity, consistent with the interpretation that
SNe with higher ejecta masses would produce more Ni. Comparing the
and the maximum luminosity, L\, distribution of a sample of SNe~Ia to
predictions from a wide range of explosion models we find an indication that
the sub-Chandrasekhar mass models span the range of observed values. However,
the bright end of the distribution can be better explained by Chandrasekhar
mass delayed detonation models, hinting at multiple progenitor channels to
explain the observed bolometric properties of SNe~Ia. iPTF16abc appears to be
consistent with the predictions from the M models.Comment: 13 pages, 8 figures, accepted for publication in MNRA
On the origin of trisomy 21 Down syndrome
Background: Down syndrome, characterized by an extra chromosome 21 is the most common genetic cause for congenital malformations and learning disability. It is well known that the extra chromosome 21 most often originates from the mother, the incidence increases with maternal age, there may be aberrant maternal chromosome 21 recombination and there is a higher recurrence in young women. In spite of intensive efforts to understand the underlying reason(s) for these characteristics, the origin still remains unknown. We hypothesize that maternal trisomy 21 ovarian mosaicism might provide the major causative factor.
Results: We used fluorescence in situ hybridization (FISH) with two chromosome 21-specific probes to determine the copy number of chromosome 21 in ovarian cells from eight female foetuses at gestational age 14–22 weeks. All eight phenotypically normal female foetuses were found to be mosaics, containing ovarian cells with an extra chromosome 21. Trisomy 21 occurred with about the same frequency in cells that had entered meiosis as in pre-meiotic and ovarian
mesenchymal stroma cells.
Conclusion: We suggest that most normal female foetuses are trisomy 21 ovarian mosaics and the maternal age effect is caused by differential selection of these cells during foetal and postnatal development until ovulation. The exceptional occurrence of high-grade ovarian mosaicism may
explain why some women have a child with Down syndrome already at young age as well as the associated increased incidence at subsequent conceptions. We also propose that our findings may explain the aberrant maternal recombination patterns previously found by family linkage analysis
High-performance network traffic processing systems using commodity hardware
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-36784-7_1The Internet has opened new avenues for information ac-
cessing and sharing in a variety of media formats. Such popularity has
resulted in an increase of the amount of resources consumed in backbone
links, whose capacities have witnessed numerous upgrades to cope with
the ever-increasing demand for bandwidth. Consequently, network tra c
processing at today's data transmission rates is a very demanding task,
which has been traditionally accomplished by means of specialized hard-
ware tailored to speci c tasks. However, such approaches lack either of
exibility or extensibility|or both. As an alternative, the research com-
munity has pointed to the utilization of commodity hardware, which may
provide
exible and extensible cost-aware solutions, ergo entailing large
reductions of the operational and capital expenditure investments. In
this chapter, we provide a survey-like introduction to high-performance
network tra c processing using commodity hardware. We present the
required background to understand the di erent solutions proposed in
the literature to achieve high-speed lossless packet capture, which are
reviewed and compared
iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernova
We report the discovery of a multiply-imaged gravitationally lensed Type Ia
supernova, iPTF16geu (SN 2016geu), at redshift . This phenomenon could
be identified because the light from the stellar explosion was magnified more
than fifty times by the curvature of space around matter in an intervening
galaxy. We used high spatial resolution observations to resolve four images of
the lensed supernova, approximately 0.3" from the center of the foreground
galaxy. The observations probe a physical scale of 1 kiloparsec, smaller
than what is typical in other studies of extragalactic gravitational lensing.
The large magnification and symmetric image configuration implies close
alignment between the line-of-sight to the supernova and the lens. The relative
magnifications of the four images provide evidence for sub-structures in the
lensing galaxy.Comment: Matches published versio
R-band light-curve properties of Type Ia supernovae from the (intermediate) Palomar Transient Factory
We present the best 265 sampled R-band light curves of spectroscopically identified Type Ia supernovae (SNe) from the Palomar Transient Factory (PTF; 2009-2012) survey and the intermediate Palomar Transient Factory (iPTF; 2013-2017). A model-independent light-curve template is built from our data-set with the purpose to investigate average properties and diversity in our sample. We searched for multiple populations in the light-curve properties using machine learning tools. We also utilized the long history of our light curves, up to 4000 days, to exclude any significant pre- or post- supernova flares. From the shapes of light curves we found the average rise time in the R band to be 16.8+0.5-0.6 days. Although PTF/iPTF were single-band surveys, by modelling the residuals of the SNe in the Hubble-Lemaître diagram, we estimate the average colour excess of our sample to be E(B - V)‰ ≈ 0.05(2) mag and thus the mean corrected peak brightness to be M R = -19.02 ± 0.02 +5 log (H0[km, s-1 Mpc-1]/70) mag with only weak dependennce on light-curve shape. The intrinsic scatter is found to be σ R = 0.186 ± 0.033 mag for the redshift range 0.05 < z < 0.1, without colour corrections of individual SNe. Our analysis shows that Malmquist bias becomes very significant at z = 0.13. A similar limitation is expected for the ongoing Zwicky Transient Facility (ZTF) survey using the same telescope, but new camera expressly designed for ZTF
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Spectroscopy of the first resolved strongly lensed Type Ia supernova iPTF16geu
We report the results from spectroscopic observations of the multiple images of the strongly lensed Type Ia supernova (SN Ia), iPTF16geu, obtained with ground-based telescopes and the Hubble Space Telescope (HST). From a single epoch of slitless spectroscopy with HST, we resolve spectra of individual lensed supernova images for the first time. This allows us to perform an independent measurement of the time-delay between the two brightest images, Δt = 1.4 ± 5.0 d, which is consistent with the time-delay measured from the light curves. We also present measurements of narrow emission and absorption lines characterizing the interstellar medium in the SN Ia host galaxy at z = 0.4087, as well as in the foreground lensing galaxy at z = 0.2163. We detect strong Na ID absorption in the host galaxy, indicating that iPTF16geu belongs to a subclass of SNe Ia displaying ‘anomalously’ large Na ID column densities compared to dust extinction derived from light curves. For the lens galaxy, we refine the measurement of the velocity dispersion, σ = 129 ± 4 km s⁻¹, which significantly constrains the lens model. We use ground-based spectroscopy, boosted by a factor ∼70 from lensing magnification, to study the properties of a high-z SN Ia with unprecedented signal-to-noise ratio. The spectral properties of the supernova, such as pseudo-Equivalent widths of several absorption features and velocities of the Si II-line, indicate that iPTF16geu is a normal SN Ia. We do not detect any significant deviations of the SN spectral energy distribution from microlensing of the SN photosphere by stars and compact objects in the lensing galaxy
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